@hammermalc I don't know about the rope yet, or the green wire cutters, cheese, magnet, or dynamite
The gold key door is hidden, as Grandad mentioned earlier it's another combination puzzle. Answer: You have two buttons behind the doors (the yellow flower button is used to unlock an unrelated shortcut so ignore that) On the new platforms after pressing the buttons in the silver and steel rooms you need to press the right sequence on each of the platforms. There's obviously a clue for it somewhere, but I got it through trial and error again. You'll know if you've gotten a part of the combination correct as a hole will open up. If you mess up you'll have to start over.
This is as far as I've gotten now as I only have one dart, I'm missing the other two apparently.